TVA issues Shawnee findings ahead of decision on two coal units

Ahead of a Dec. 30 Board of Directors meeting where this matter is due to be decided, the Tennessee Valley Authority on Dec. 23 released a finding of no significant impact related to a final environmental assessment covering clean-air options for units at the Shawnee coal plant.

In April 2011, TVA and the U.S. Environmental Protection Agency entered into a Federal Facilities Compliance Agreement to resolve a dispute over how the Clean Air Act’s New Source Review program applied to maintenance and repair activities at TVA’s coal-fired power plants. TVA also entered into a substantially similar judicial consent decree with four states and three environmental advocacy organizations.

These agreements require TVA to, among other things, reduce emissions from its coal-fired power plants. At its Shawnee Fossil Plant (SHF) Units 1 and 4, TVA must decide whether to install and continuously operate selective catalytic reduction (SCR) and flue gas desulfurization (FGD) systems, repower the units to burn renewable biomass, or retire the units by Dec. 31, 2017. TVA must inform EPA and the other consent decree parties of its decision for Units 1 and 4 by Dec. 31, 2014.

If TVA decides to control the units or convert them to biomass, the agreements provide TVA the discretion to change the decision to retirement later. TVA proposes to comply with the EPA Clean Air Agreements provisions for SHF Units 1 and 4 by installing and operating SCR systems to reduce nitrogen oxide (NOx) emissions and FGD systems to reduce sulfur dioxide (SO2) emissions.

The proposed action is the subject of the final environmental assessment (EA) prepared by TVA in accordance with the National Environmental Policy Act. The EA evaluates the No Action Alternative and two action alternatives in detail.

  • Under the No Action Alternative (Alternative A), TVA would continue to operate SHF Units 1 and 4 without implementing measures to reduce SO2 and NOx emissions to comply with the EPA Clean Air Agreements. To stay in compliance, TVA would have to retire the units by Dec. 31, 2017, unless the agreements are revised. The No Action Alternative would not meet the identified purpose and need and is considered unreasonable.
  • Under Alternative B, TVA would retire the two units by Dec. 31, 2017.
  • Under the preferred Alternative C, TVA would install and operate the SCR and FGD systems on Units 1 and 4.

All of the construction activities under Alternatice C would occur in heavily disturbed areas. The SCR systems would be installed in the location of the non-operational electrostatic precipitators which would be removed. The 250-foot tall original emission stacks for Units 1 and 4 would be demolished and the new FGD systems would be located in the area of these stacks. Additional actions include changes to the dry fly ash piping systems, extensions of on-site electrical components, construction of an ammonia receiving and storage facility, and construction of FGD reagent preparation and feed systems.

The FGD systems would be dry systems using calcium hydroxide as the reagent. Coal combustion residuals (CCRs) from Units 1 and 4, consisting of ash and scrubber residue, would be comingled and trucked to the existing onsite dry stack for disposal. SHF Units 2-3 and 5-9 would not be affected by the proposed action.

TVA also considered converting the two units to biomass, but determined that was too costly and infeasible.

SHF is located adjacent to the Ohio River about 10 miles northwest of Paducah, Ky. Construction of the ten similar pulverized coal units began in 1951. Unit 10 was converted from a pulverized coal boiler to a 124-MW atmospheric fluidized bed boiler in the 1980s; it was removed from service in 2010 and formally retired in 2014. The nine active coal-fired units have a summer net capability of 1,206 MW.

Emissions of air pollutants are controlled by the following:

  • Use of low-sulfur coal for reducing SO2 emissions;
  • Use of low-NOx burners for reducing NOx emissions;
  • Use of fabric filter baghouses to reduce particulate emissions;
  • Use of dry sorbent injection (DSI) systems to reduce emissions of acid gases for compliance with the Mercury and Air Toxics Standards (MATS). These systems are currently being installed and will be fully operational in 2015. They will use a calcium-based sorbent.

 

SHF burns about 9,600 tons of coal a day, which is a blend of about 75% Powder River Basin (PRB) subbituminous coal and 25% Colorado bituminous coal.

The relatively small generating units at SHF, approximately 134 MW each, are operated on Automatic Generation Control and can be started up and shut down relatively quickly to respond to changes in energy demand. They provide TVA the flexibility to operate SHF for baseload power, when the units operate at or close to their maximum capacity most of the time, and intermediate-load power, when the units change their output as energy demand increases and decreases over time (usually during the course of a day). The TVA system benefits from the small, flexible, and load-following resource characteristics of these units. 

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.